Some friends of mine are planning to use my small basement shop to put together a dome, and looking through the plans the two things I see as being the biggest pains are:
* cutting 100+ lengths of EMT
* flattening the ends of the EMT

For cutting EMT I typically use a typical hand tubing cutter, but then most of my household projects don't require more than a couple of cuts.Using this (or a hacksaw) for several hundred cuts would be really tedious, so I figured I'd ask for suggestions here. Would it be possible to use a heavy duty power saw (either a mitre or table saw) for this? I could definitely use a jig saw with a metal cutting blade for this but it'd be slower and less accurate.

For flattening my only good thoughts are squeezing it in a vice or hitting it with a sledge hammer, the first seems slow and tedious and the second wouldn't be very accurate. I imagine I could throw together some sort of jig to improve the sledgehammer option, but this is clearly another problem many people here have dealt with.

When I built my dome I cut all the struts with a hacksaw. The best tool to use in my opinion is a band saw. A table saw would probably work but if it catches it might fling the pipe at you so you'd definitly want it clamped down and be sure to use a blade for cutting metal, not wood. Metal saw blades have smaller teeth. It would be well worth your time to get a hold of a band saw.

For flattening the ends, I knew someone with access to a metal shop, so I used a press. It worked great. The longer the handle the better. A sledgehammer or a single jack would work. You'd have much more control with a single jack, but you might have to pound on it a couple times.

For drilling the holes I used a drill press, but a hand drill would work just as good.

I've read that an abrasive blade with a chop saw could do this, but that the single speed nature of my saw might now cut it. Any thoughts on that? I've also been reading that a reciprocating saw (ie Sawzall) might work well, I actually have one that I haven't used in ages that I could get new blades for.

I use a portable bandsaw to cut the EMT and to flatten the ends I made a
portable press that uses a 10 ton air over hydrualic jack with a set of
dies I made. Then a drill press to drill the bolt holes.

ragabashpup wrote:back over them with an ambulance when they are getting out to help someone.

Awesome!!

You can get metal cutting blades for a jigsaw and it should cut EMT very easily. Otherwise, if you have a chop saw I would just get the thin-est abrasive blade you can find that will fit it. There will be sparks and there will be some smoke. But it will be a huge time saver. If you have a neighbor with a bandsaw, make friends with them.

Arbor press, vice, or a mini sledge to flatten. The mini sledge will come in handy on the playa for driving rebar into the ground.

While I haven't cut a lot of metal tubing, what I have cut has been on my chop saw and it sailed through 6 or 8 bundled together like it was nothing.

While yes, they will cut through it, I'm thinking a sawzall or jig saw are not going to be good options without some kind of jig or vise holding the conduit in place and steady. A sawzall is good for tearing shit apart and making big stuff into little stuff, but not real good at precision cutting on small stuff due to the reciprocating nature of the blade ripping through it.

Bob wrote:Plan ahead, eg make a jig, and rent equipment at your local equipment rental yard.

Yep. Mark all your conduit cuts ahead of time. A half day rental on a metal chop saw should be fairly inexpensive and will save you a tremendous of grief. They will typically measure the chop blade and you'll pay a small fee on top of the rental for however much of the blade is used in the process.

You'll need a metal-cutting blade, don't forget! Before I got a chop saw I used to cut my struts with a Sawzall (with metal blade!) by leaving the bundles of EMT bound together so they didn't wiggle. Fairly accurate for 2V domes, where you can have up to a 1" slop factor without even noticing. I don't like using pipe cutters because A) they're tedious and B) they leave a REALLY sharp inner edge which I always slice myself on while feeling for the weld-seam.
Why feel for the weld seam? So you can make sure it's neither straight UP or straight DOWN before you smash. That way it won't tear open and make a raggedy end.

Do use a proper Jig for every step of the process, accuracy is important or it won't fit together properly.
Do Not do it by hand by guessing.

Do use a Chop Saw to cut each piece, be sure you take into consideration how wide your blade is, they aren't all the same! They are also very fast!!
Do Not use a hand held tool, it's slow.

Do use an appropriate press with an appropriate stand. 10 ton should be able to crush smaller EMT.
Do not use any hand held tools. Your ends won't be flat or parallel, both are important for the overall stability of your structure.

Do use a vertical mill/drill press. By following these simple instructions each of my struts are accurate to +- 1/100 inch. I also finished the whole project by my self in 3 days. I used a Bridgeport like this one to do the drilling:

My Bridgeport is serous overkill but its sure fast! If you buy all the "basic" equipment to do it right you would have to spend about $800. Use what you have at hand or borrow from a friend. I'm sure you are no more than a phone call away from all the equipment you need. Good luck and remember, measure twice, cut once! If you calculate it properly you should end up with no more than a few inches of wasted pipe when you are all done.

TomServo wrote:Try a tube cutter, and buy extra blades. Is nice and quiet, and won't piss of your neighbors.

I tried a pipe cutter the first few pipes. It will take you forever. In the time it takes to cut ONE pipe with a pipe cutter, I can rip through at least TEN pipes with my jigsaw. It's not nearly as loud as a chopsaw.

TomServo wrote:Try a tube cutter, and buy extra blades. Is nice and quiet, and won't piss of your neighbors.

I tried a pipe cutter the first few pipes. It will take you forever. In the time it takes to cut ONE pipe with a pipe cutter, I can rip through at least TEN pipes with my jigsaw. It's not nearly as loud as a chopsaw.

-Badger

Yes. I did all my pipe in an afternoon using my saw. Little 'tube cutters' are fine for one off cuts of pipe but you'll want to scream really quickly. Your neighbors can put up with some noise for an afternoon. It's only a few hours.

Oh, and since I finally decided to move last year's pictures from the flash drive to my computer... here's my setup. I can't emphasize enough how important a good jig is. Make sure your ends are both flattened parallel too!

The wood has a stopper (which gets moved for each end of each size pipe) so I know how far to flatten.

The Bridgeport has a little metal arm in the far left of the image that tells me exactly how far the hole is from the edge.

And he was soooo smart. He made a jig with a 2x4 so everytime was EXACT on its mark.
And yes, get a press!!!!!!!!another jig to make sure both ends are being smashed correctly...dont wanna pick one up and realize your verticle is horizontal on the other end...dude!

then again make ANOTHER jig, to mark the same exact spot to punch the bolt holes through.
The Domes have to be pretty much right on target or you will not get the strength you need.

mdmf007 wrote:Nice set up with the press. A little more work,. and you can incorporate a punch as well. Knocks out bolt holes at the same time.

If you do it that way you really need to make a jig to line things up tot he right dimension.

I looked into it but with my 20ton press I couldn't have produced enough force to cut through the conduit (and I would have had to engineer the cutting tools!) I did consider it and decided against it. My shop is well stocked but I think it would have taken something a lot bigger than a 20ton.

Oh, one more comment about all the EMT, be sure you make extras! I haven't had a single piece bend or break but on my camp's larger 40ft dome we usually destroy a few pieces each year. Make a few extras if you have a big dome!

capjbadger wrote:Ah yes, very good point. Extras... nothing worse than getting out there to only find you can't put up the dome due to one bent strut.

Also, once it's built, set it up at home a few times and figure out your covering. Not the sort of this you want to do for the first time in a 30mph whiteout duststorm.

-Badger

Haaahhheeeoooo..

I did that..

I spent ages planning everything else and I just assumed I'd "figure it out" when I got out there. It worked just fine and nothing was damaged, not even my ego. Still.. do what the good Badger says.. test it out first.

Just a word, for those WITHOUT a machine shop at their disposal OR a Harbor Freight nearby....

Two-decimal accuracy is nice, but you CAN also flatten your tube ends with a hammer and anvil if necessary. (I in fact prefer to do so.) Pay attention to what you're doing, and take breaks when your bulging biceps rip through your shirt. As an encore, tear a few phonebooks in half.

BIG second on the "test first" concept...Colorcoding your struts can help, even if you're just building a 2V- They can look the same when you're tired!

And about HARDWARE....My personal preference is for 3/8" Grade 5 nuts and bolts (bought by the pound from TSC) and silver-dollar-sized fender washers. I hand-drill my boltholes (of course!) with a stepped bit, and cut 'em 1/2" for easier fit and less damage to the bolt threads. While I find the "village blacksmith" part of the strut flattening immensely satisfying I wouldn't be as quick to recommend hand drilling-It's VERY tough on the wrists. If you choose this path, try drilling 1/8" pilot holes before switching to the 'stepper.

I used a two pound hammer and an old brake rotor from a big truck to flatten my 3/4" emt tubing. I'm frugal and found the rotor at the school I attend. It had about a 2 and half inch flat spot on the round part ...uh the outer ring flat-spot-thingy. I just put the emt tube on it at the center and started flattening it with the hammer. Then we marked the flat parts in the center with an nail set and drilled them out. It took a bit but it worked fine. Make sure the flat ends match from one end to the other.(the same plane). To angle the struts I cut out a big piece of cardboard at the angles I needed and used that as a reference. I lined up pall the struts on the ground and put a 2 by 8 over the flat parts and drove my truck onto it. My wife held the cardboard angle of to the side as i pulled up on the tubing. And we just eyeballed the angle. The dome turned out awesome for last year. No problems at all. (except the custom cover we made) I used 2 1/2 bolts. @ inch bolts would have worked but I had already had the bigger ones. We bought our emt 3/4 inch tubes at Home Depot, and they cut them perfectly for us for free!!!! I gave them a few days to do it because we bought 40 tubes. Tip the dude too.
As for the cover, we got a sweet deal on some yellow billbord vinyl.It is such a bitch making and cutting and gluing that thingo fit. It's round and nothing is flat you know... I am so thankful my wife is a math major and knows how to do the adding or whatever magic math thing she did. It fits perfect and NO dust! weird not having dust where we crashed and had our stuff! Let me know If you need the specs and or pictures.

We don't have an easy billboard vinyl source her in 'Kazoo, but I have LOTS of "Sunbrella" marine acrylic banner fabric left over from my brief tenure as a screen printer. Just been too lazy to sew ten zillion triangles together until now, but you inspire me, Sir!